CVE-2011-2503 in systemtap
Summary
by MITRE
The insert_module function in runtime/staprun/staprun_funcs.c in the systemtap runtime tool (staprun) in SystemTap before 1.6 does not properly validate a module when loading it, which allows local users to gain privileges via a race condition between the signature validation and the module initialization.
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Analysis
by VulDB Data Team • 12/07/2021
The vulnerability described in CVE-2011-2503 resides within the systemtap runtime tool's staprun component, specifically in the insert_module function located in runtime/staprun/staprun_funcs.c. This flaw represents a critical security issue affecting SystemTap versions prior to 1.6, where the system fails to properly validate kernel modules during the loading process. The vulnerability stems from insufficient input validation mechanisms that allow malicious local users to exploit a race condition inherent in the module loading sequence, potentially enabling privilege escalation attacks.
The technical implementation of this vulnerability involves a race condition between signature validation and module initialization phases within the staprun utility. During the module loading process, the system performs signature verification before module initialization, but this validation occurs in a non-atomic manner. Attackers can exploit this timing gap by manipulating the module loading sequence to bypass signature checks, effectively allowing arbitrary kernel modules to be loaded with elevated privileges. This race condition directly maps to CWE-367, which addresses Time-of-Check to Time-of-Use vulnerabilities, where the system's validation occurs at a different point in time than when the actual operation is performed.
The operational impact of this vulnerability is significant for systems utilizing SystemTap for performance monitoring and debugging purposes. Local attackers with basic user privileges can leverage this flaw to load malicious kernel modules, potentially gaining root access or executing arbitrary code with kernel-level privileges. This privilege escalation vector is particularly dangerous because it operates at the kernel level, bypassing traditional user-space security controls and potentially allowing attackers to establish persistent backdoors, modify system behavior, or extract sensitive information from the kernel space. The vulnerability affects systems where SystemTap is installed and actively used for kernel module management.
Mitigation strategies for CVE-2011-2503 require immediate system updates to SystemTap version 1.6 or later, which contains the necessary fixes for proper module validation. Organizations should also implement additional security controls such as restricting access to staprun functionality, disabling unnecessary kernel module loading capabilities, and monitoring for suspicious module loading activities. The fix addresses the race condition by ensuring atomic validation and initialization processes, preventing the timing window that attackers could exploit. This vulnerability demonstrates the importance of proper input validation and atomic operations in kernel-level code, aligning with ATT&CK technique T1068 which covers local privilege escalation through kernel exploits. System administrators should also consider implementing kernel module signing requirements and monitoring for unauthorized module loading activities to reduce the attack surface and detect potential exploitation attempts.